If TV manufacturers were doing their job well, there would be little use for the new Roku 3 streaming-video set-top box.

Just about every set maker has its own “smart-TV” system for connecting to the Internet to access programs from Netflix and other online services.

And just about every one of these “smart TVs” is pretty stupid, with clumsy interfaces, limited choices and sometimes painful setup processes. The most recent one I grappled with, a Panasonic, had me debugging DHCP problems. If you don’t know what that means, trust me, you’re better off.

By contrast, the $100 Roku is a model of simplicity and choice, with a relatively painless setup process and a new, easier-to-navigate interface.

Getting up and running with the unobtrusive, hockey-puck-like Roku 3 took me about 20 minutes. I connected it to an HDMI input on my TV, plugged it in and, following the on-screen instructions, introduced it to my Wi-Fi network. (There’s also an Ethernet port for wired networks.)

The most laborious part of the process was enabling my existing programming services, which required me to log in to each one through a Web browser on my computer or mobile device and enter a code generated by the Roku on the TV screen.

Unfortunately, Roku comes with its own remote — no one wants yet another remote to juggle. But Roku’s has something to ease the pain: a headphone jack. Plug in a headset, and the TV’s speakers are immediately silenced as the audio output is transferred to the remote.

Silent viewing

It’s a neat feature, allowing you to watch in bed without the sound disturbing a sleeping partner. Roku even includes a set of earbuds, though I would have preferred the company skip them — I have enough of those already — and instead include the HDMI cable you’ll need.

A number of companies make products that access online programming, including Western Digital (the WD TV Play) and D-Link (the Boxee Box). But Roku’s most important competitor by far is the $99 Apple TV, which offers fewer choices but better integration with Apple devices and content — including the ability, through Apple’s AirPlay technology, to stream movies and TV shows directly from computers and iDevices.

Wi-Fi scheme

Roku is working on adding a similar feature, using a new Wi-Fi scheme called Miracast, but no telling how long that will take or what devices it will work with.

Both boxes offer access to pay services including Netflix, Major League Baseball games and Hulu Plus. And each has some important video sources missing from the other: Amazon Instant Video only on Roku, iTunes and Google’s YouTube only on Apple TV.

But Roku has a far larger selection, more than 700, the company says, many of them free and/or highly specialized in nature: the Indian Food channel; Hypnosis TV; and Rustavi 2, which provides “a diverse range of top quality TV programming” in “the native language of the Republic of Georgia.”

It also comes with the “Angry Birds in Space” game built in, the remote doubling as a handheld controller.

In terms of performance, the Roku 3 has a more powerful processor and better Wi-Fi than its top-of-the-line predecessor, the Roku 2 XS. I’m not sure how much difference that makes in practical terms, since I never had serious performance issues with previous models, but it may allow for additional capabilities later.

Hi-def streaming

Like the 2 XS and the $80 2 XD, the new Roku streams video at up to 1080p full high-definition. (Two cheaper models, the $50 LT and $60 HD, top out at 720p.) The new interface is indeed less cumbersome than the old one — it will be offered on the previous models as a software update — and moves along smoothly on the 3.

There are, of course, many other ways to connect your TV to the Internet, including via gaming consoles like Microsoft’s Xbox and Sony’s PlayStation.

Every one of them poses the implicit question: Why should you need a separate device at all?

But until the TV makers get smarter about smart TVs, or Apple delivers its long-rumored set, Roku is one of the easiest and most elegant ways to add intelligence.